Method for producing a building material granulate on the basis of mineral grains

Abstract

The invention relates to a building material granulate on the basis of mineral grains in the form of fine sand grains and / or desert sand grains, in which a proportion of broken grain of desert sand and / or a proportion of broken grain of fine sand is / are incorporated in a hydraulically bonded binder matrix. The invention further relates to a method for producing a building material granulate on the basis of mineral grains in the form of fine sand grains and / or desert sand grains in which broken grain of desert sand and / or broken grain of fine sand is / are provided and a proportion of the broken grain of desert sand and / or a proportion of the broken grain of fine sand is / are granulated with a proportion of a granulation agent forming a hydraulically binding binder matrix.

Description

[0001] The invention relates to a method for producing a building material granulate based on mineral grains in the form of fine sand grains and / or desert sand grains.

[0002] Sand and gravel are essential components of concrete. Due to the growth of the construction industry, particularly in emerging markets, the necessary quantities of sand for concrete production are often no longer available in sufficient quantities, resulting in some countries having to rely on sand and gravel imports. Due to the global shortage of suitable sand for concrete production, previously unused resources such as desert sand or surplus fine sand are increasingly coming into focus. To date, the fine sand components contained in the sand fractions have largely been separated and flushed back into the gravel extraction areas. In Germany alone, the resulting unused and thus landfilled fine sand amounts to up to 40 million tons per year. Furthermore, the landfilled fine sand components cause considerable environmental damage.The grain structure of fine sands and desert sands is characterized by a rounded geometry and a smooth surface. Due to this nature, fine sands and desert sands are unsuitable for the production of concrete.

[0003] State-of-the-art processes involve producing so-called polymer concretes from fine sand by bonding the individual sand grains with, for example, polyester resins, methyl methacrylate resins, epoxy resins, or other reactive resins. A corresponding process is known, for example, from DE 20 2006 012 396 U1.

[0004] According to the teaching of DE 10 2015 114 554 A1, desert sand is solidified with water glass in combination with polymer sulfur and microcrystalline silica to produce artificial sandstone.

[0005] DE 10 2014 006 942 B3 discloses a process in which the round grain structure of desert sand is converted into an angular grain structure through thermal treatment, making the sand suitable for concrete production. DE 32 48 537 C2 discloses a process in which an aggregate suitable for the concrete industry is produced by sintering desert sand at temperatures of up to 1600 °C. However, due to the required temperatures, this is a comparatively cost- and energy-intensive process, making it unsuitable for the mass production of aggregates required for the concrete industry.

[0006] CN 105 036 651 A describes a process for producing concrete using untreated desert slag as an aggregate.

[0007] WO 2016 / 188559 describes a process for producing a polymer concrete using desert sand as aggregate.

[0008] The object underlying the present invention is to enable a cost-effective use of desert sands for the construction industry.

[0009] According to the invention, the object is achieved by a method according to claim 1. Advantageous embodiments and further developments of the invention can be realized with features defined in subordinate claims.

[0010] According to the concept of the invention, aggregates with smooth or rounded surfaces, such as those found in desert sand grains and / or fine sand grains, are made available for use in the form of building material granules for concrete production. According to the invention, a crushed grain of desert sand is used. A crushed grain of desert sand can preferably be achieved by grinding in a grinder. For the purposes of the invention, a crushed grain is primarily understood to mean a ground grain.

[0011] In this mineral-based construction granulate in the form of desert sand grains, a portion of crushed desert sand is incorporated into a hydraulically set binder matrix. By incorporating the crushed desert sand grains into a binder matrix, desert sand-based materials can be produced that are suitable for further processing in the construction industry. The construction granulate can be stored in bulk.

[0012] Advantageously, the binder matrix contains at least one hydraulic binder such as cement and / or at least one latent hydraulic binder, which holds / holds the building material granules together in the set state and thereby binds the portion of the broken grain of desert sand into the structure of the building material granules.

[0013] In the case of the building material granulate, it can be provided that the proportion of crushed grain of desert sand has a grain size spectrum of up to 0.125 mm.

[0014] By definition, the fine sands used can have grain sizes between 0 mm and 0.2 mm.

[0015] Advantageously, the building material granulate can have a total proportion of untreated mineral grains, i.e. unbroken round, smooth mineral grains in the form of fine sand grains and / or desert sand grains, of up to 50 percent by mass.

[0016] In contrast to desert sands, unwashed fine sands usually contain grains smaller than 0.063 mm, which has a beneficial effect on granulation, as smaller grain sizes promote agglomeration.

[0017] It may therefore be provided that a total proportion of up to 50 mass percent of an unbroken grain size of mineral grains, which includes an unbroken grain size of desert sand and / or an unbroken grain size of fine sand, is incorporated into the binder matrix of the granulate.

[0018] The building material granules of the building material granulate can preferably have a size range up to a diameter of 16 mm, preferably up to a diameter of 8 mm. Depending on the granulation process or the granulation or pelletizing system, the granules can have a substantially round or a substantially cylindrical shape. The granules according to the invention can also be referred to as pellets.

[0019] In the method according to the invention for producing a building material granulate based on round, smooth mineral grains in the form of desert sand grains, a crushed grain of desert sand is provided. The crushed grain of desert sand can preferably be prepared by grinding in a grinder. A portion of the crushed grain of desert sand is granulated with a portion of a granulating agent that forms a hydraulically setting binder matrix. After granulation, a drying step can be provided, whereby the resulting granules can dry separately from one another.

[0020] According to the concept of the inventive process, round, smooth mineral grains in the form of desert sand grains are first ground, providing a crushed grain structure. A portion of the crushed desert sand grains is then mixed with a granulating agent that forms a hydraulically setting binder matrix, and granulated, binding the crushed desert sand grains into granules.

[0021] The granulation of the mixture of a portion of the crushed grain of desert sand and the granulating agent can be carried out by means of a granulating plant or pelletizing plant as known from the state of the art.

[0022] Preferably, a grain size spectrum of crushed desert sand with a grain size of up to 0.125 mm can be used. The grain size of the desert sand grains can be influenced by crushing or grinding in the grinder.

[0023] According to an advantageous embodiment of the method according to the invention, a crushed grain of desert sand with a grain size of less than 1 mm is used during granulation, whereby the proportion of grains smaller than 75 µm should be at least 25 percent.

[0024] Furthermore, according to an advantageous embodiment of the method according to the invention, it can be provided that an unbroken grain of a fine sand, which consists of at least 30% grains with a grain size of less than 1 mm, is granulated directly with the granulating agent. In this case, small proportions of unbroken grains up to a maximum grain size of 2 mm can be granulated.

[0025] According to one embodiment of the method according to the invention, it can further be provided that the granulating agent comprises at least one hydraulic binder and / or at least one latent hydraulic binder and water, wherein the at least one hydraulic binder and / or the at least one latent hydraulic binder and the water are added separately during granulation. According to a preferably simple embodiment, cement and water can be used as granulating agents. Granulation can be carried out in such a way that the portion of the crushed grain of desert sand is first provided on a granulating plate or granulating disk. The portion of the crushed grain of desert sand is then sprayed with water and the portion of cement is added.Through circular movements of the granulating disc or plate, the crushed desert sand, water, and cement are mixed and formed into granules. According to one example, a ratio of 7 parts crushed desert sand, 3 parts cement, and 1 part water can be used for granulation.

[0026] According to a further advantageous embodiment of the method according to the invention, it can be provided that the granulating agent comprises a binder suspension formed from at least one hydraulic binder and / or at least one latent hydraulic binder and water, which is provided separately. In this embodiment, the portion of the crushed grain of desert sand is mixed with a binder suspension and granulated. The binder suspension is a mixture of water and a hydraulic binder, preferably cement, which is suspended under the action of high shear forces. Advantageously, a portion of the cement required for the binder suspension can be replaced by a latent hydraulic binder.Furthermore, it may be intended that a portion of the crushed desert sand grains with a grain size of up to 0.125 mm be used in the preparation of the binder suspension. This makes it possible to utilize a portion of the crushed desert sand grains as a cement substitute in the binder suspension intended as a granulating agent.

[0027] The use of the binder suspension prepared in high-performance mixers as a granulating agent has the advantage of achieving a particularly high level of homogeneity, which has a positive impact on the standardization of quality parameters such as compressive strength, particle size distribution and surface quality of the granules produced.

[0028] Advantageously, the quality of the produced granules can be achieved by varying the composition of the granulating agent. This allows quality changes or adjustments to be made beyond the usual range of state-of-the-art options for changing technological parameters in granulation plants, such as residence time, rotational speed, or temperature.

[0029] Furthermore, according to the method according to the invention, at least one additive selected from a group comprising: a flow agent, a concrete plasticizer, an air-entraining agent, a setting accelerator, a stabilizer, and a sealant can be used during granulation. The at least one additive can be added separately during granulation or mixed into the separately provided binder suspension of the granulating agent.

[0030] It has been shown that by admixing an unbroken grain size of mineral grains comprising an unbroken grain size of desert sand and / or an unbroken grain size of fine sand, up to a ratio of 50 mass percent, stable granules can be provided using the process according to the invention, which are suitable as bulk material for soil compaction or as aggregate in concrete production. It can therefore be provided that an additional proportion of an unbroken grain size of mineral grains comprising an unbroken grain size of desert sand and / or an unbroken grain size of fine sand is used during granulation, up to a total proportion of 50 mass percent.

[0031] The invention relates to a method for producing a building material granulate based on mineral grains in the form of desert sand grains, in which a crushed grain of desert sand is provided and a portion of the crushed grain of desert sand is granulated with a portion of a granulating agent forming a hydraulically setting binder matrix.

Claims

1. A method for producing a granulated building material based on mineral grains in the form of desert sand grains, wherein a broken graining of desert sand is provided and a fraction of the broken graining of desert sand is granulated with a fraction of a granulation means forming a hydraulically binding binder matrix.

2. The method according to claim 1, characterised in that the broken graining of desert sand is provided by grinding in a grinder.

3. The method according to any one of claims 1 or 2, characterised in that a grain spectrum of the broken graining of desert sand with a grain size of up to 0.125 mm is employed.

4. The method according to any one of claims 1 to 3, characterised in that the granulation means comprises at least one hydraulic binder and / or at least one latent hydraulic binder and water, wherein the at least one hydraulic binder and / or the at least one latent hydraulic binder and the water are added separately during granulation.

5. The method according to any one of claims 1 to 3, characterised in that the granulation means comprises a binder suspension formed from at least one hydraulic binder and / or at least one latent hydraulic binder and water which is provided separately.

6. The method according to any one of claims 1 to 5, characterised in that during granulation, at least one additive is employed, which is selected from a group, comprising: a flow agent, a concrete liquefier, an air-entraining agent, a solidification accelerator, a stabilisation agent, a sealing agent.

7. The method according to any one of claims 1 to 6, characterised in that during granulation, a fraction of an unbroken graining of mineral grains, which comprises an unbroken graining of desert sand and / or an unbroken graining of fine sand, up to a total fraction of 50 percent by mass is additionally employed.